1. Field of the Invention
This invention relates, in general, to dot matrix print heads utilizing print wires and, more particularly, to the linear bearings supporting the print wires.
2. Description of the Prior Art
The principal cause of failure of print heads of the dot matrix type utilizing print wires reciprocal within tubular linear bearings is the migration of ink from the ribbon into the bearings. The ink, which is adsorbed on the wires as they impact the ribbon, moves along the length of the print wire into the tubular bearing of the end guide and on into the housing and the linear bearings of internal guides where it congeals. The congealed ink eventually produces sufficient friction within the bearings to cause faulty impact between the print wire and the ribbon; slow return resulting in snagging of the ribbon; and bending or breaking of the print wires. Heretofore, there was no known way to prevent this problem.
Another problem with existing print wire bearings is the friction between the print wire and the linear bearing resulting in wear on both the print wire and the bearing resulting in poor performance of the print head.
While several inventions, as typified by U.S. Pat. No. 4,044,668, issued to G. B. Barrus et al, and U.S. Pat. No. 4,571,101, issued to A. Sakaida et al, utilize air flow within printer housings for cooling purposes, no inventions are known which provide gas flow through linear bearings to prevent ink migration along print wires nor are any inventions known which provide gas bearings for the support of print wires.